The instructions happen on WhatsApp and stay there
The work gets done, the record never leaves somebody's phone, and the account pays for it.
What's happening?
The instruction arrives as a voice note, a photo of a sketch, a crack on with it at the end of a thread. The work gets done, because that is what sites do. The record stays on one person's phone, mixed in with everything else, unfiled and unsearchable, and when that person changes jobs or changes handset, the only evidence of who ordered what goes with them.
Most contracts want instructions in writing, or confirmed in writing when they are given by word of mouth. A message can count as writing, but a message nobody can find, tied to a person rather than the job, is no use to a valuation. At the account, the work is visible and the authority for it is not, and work without visible authority is where the discounting starts.
The fix is not banning the phones; sites run on them. It is a small routine that lifts the instruction off the phone the same day: message to confirmation, confirmation to the job's own record, so every crack on becomes something the account can rely on. Set up once, and checked monthly so it does not fade when the job gets busy.
The solution
A routine that lifts the instruction off the phone the day it lands.